The invention relates to a drilling apparatus and method whereby the plural cutting bits of the apparatus may be repositioned following wear caused by drilling to present fresh sharpened faces without the necessity for removing the drilling apparatus from the well.
Prior U.S. Pat. No. 1,938,412 discloses a well drilling tool including a bit having a cutting part which can be automatically advanced relative to its support to compensate for wear caused by drilling. The arrangement disclosed in this patent is dependent upon coordinated fluid pressure and spring-biasing means for the cutting part of the bit and for this reason is not desirable for the types of drilling operations which the present invention must encounter. The present invention differs drastically in its mode of operation from U.S. Pat. No. 1,938,412 in that the invention includes a positive acting repositioning means for the worn bits responding to a deliberate action by the drilling operator without dependency on springs or other automatic biasing means and without the necessity for removing the drilling apparatus from the well.
Another U.S. Pat. No. 2,198,849 discloses a drill bit having rolling type abraiding cutters and additional spring-urged blades but totally lacking the operational capabilities of the present invention.
Still another U.S. Pat. No. 3,075,593 discloses a drill bit having plural cutting elements which are removable and replaceable after becoming worn, but this arrangement requires total removal of the drilling bit from the well.